In the medical field, ultrasound diagnostic apparatuses are being used. An ultrasound diagnostic apparatus is a device that transmits and receives ultrasound to and from a living body, and forms an ultrasound image based on a reception signal obtained by the transmission and reception of the ultrasound. The transmission and reception of the ultrasound are executed by an ultrasonic probe. Various probes are commercialized, including a body cavity insertion type probe. The body cavity insertion type probe is inserted into the esophagus, the rectum, the vagina, or the like, and transmits and receives the ultrasound inside the body. Of these, the esophagus probe is a probe inserted into the esophagus, and more specifically, is a probe that transmits and receives ultrasound to and from the heart, while in the esophagus.
In recent years, three-dimensional ultrasound diagnosis is becoming more wide-spread. In this technique, ultrasound is transmitted and received to and from a three-dimensional space in a living body, to acquire volume data, and the volume data are used to form a three-dimensional image representing the three-dimensional space, a two-dimensional tomographic image representing an arbitrary cross section of the three-dimensional space, or the like. In order to transmit and receive the ultrasound to and from the three-dimensional space, in a probe head, in general, a two-dimensional array transducer is provided. The two-dimensional array transducer is formed by a plurality of transducer elements (for example, a few thousand transducer elements) arranged two-dimensionally.
Patent Document 1 discloses an esophagus probe for three-dimensional ultrasound diagnosis. A transducer unit is placed in the head of the esophagus probe. The transducer unit comprises a two-dimensional array transducer, an interface layer, an electronic circuit (integrated circuit), a backing layer, a heat sink, or the like, provided in that order from the side of a living tissue. The electronic circuit is a circuit that executes channel reduction; that is, a circuit for reducing the number of signal lines. The heat sink is a circuit that takes away heat generated in the electronic circuit.